Tricyclic nitrogen-rich explosives with a planar backbone: bis(1,2,4-triazolyl)-1,2,3-triazoles as potential stable green gas generants

Two tricyclic nitrogen-rich compounds, 4,5-bis(5-nitro-1H-1,2,4-triazol-3-yl)-2H-1,2,3-triazole (4) and 4,5-bis(5-nitramino-1,2,4-triazole-3-yl)-2H-1,2,3-triazole (5), were obtained based on the combination of two different triazole heterocycles. The metal-free energetic salts (6-16) were synthesized with positive heat of formation and good thermal stability. Among these salts, dicarbohydrazide salt 9 and triaminoguanidine salt 16 exhibit the relevant high detonation velocities (9: D = 8720 m s(-1) and 16: D = 8748 m s(-1)) which are comparable to that of RDX (8795 m s(-1)). Besides, the impact and friction sensitivities of compounds 4-16 (IS: 28-40 J, FS: 324-360 N) indicate that they have low sensitivities to mechanical stimulations. The planar structure of crystal 4 center dot 3H(2)O was confirmed by single crystal X-ray analysis. In order to evaluate their gas production capacities, constant-volume combustion experiments were conducted on 9 and 16 with high gas production volume (>= 840 dm(3) kg(-1)). The maximum gas-production pressures of 9 (P-max = 16.20 MPa) and 16 (P-max = 11.21 MPa) are much higher than that of commonly used gas generant guanidine nitrate (GN: P-max = 4.20 MPa).